Lab case 383 interpretation

Question 1:

Ph = 7.549, that is alkalaemia.

pCO2 = 24.1 mmHg, then it is respiratory alkalosis.

Next, we will calculate the compensation. From the story, the condition is acute. For acute respiratory alkalosis we expect HCO3 to drop by 2 for every 10 pCO2 less than 40.

Accordingly, expected HCO3 for this patient should be: 24 – (15.9 x 0.2) = 20.82, this is very close to the value that we have here. Possibly it is fully compensated.

We stated possibly because the anion gap for this patient was elevated. It is important to calculate the anion gap in all cases. For this patient AG = 140 – (104+21) = 15. This patient has HAGMA.

In the presence of lactate level more than 5, then that is associated with HAGMA. This patient’s lactate level was 6 mmol/L.

Other abnormal findings are:

  • Hb = 81 g/L – severe anaemia
  • Glucose = 10.1

The reason this patient’s blood gases interpretation showed we compensated respiratory acidosis because he had HAGMA and Metabolic alkalosis due to dehydration (Contraction), these 2 conditions balanced each other.

The presence of creatinine level to the high side supports the presence of contraction alkalosis.

This patient had active bleeding that caused anaemic hypoxia and reduced blood volume this led to high lactate and the kidney response to reduce blood flow is by absorbing Na in association with HCO3.

Next, we will look at the causes of respiratory alkalosis, for that we will use the mnemonic CHAMPS:

  • C = CNS diseases
  • H = Hypoxia
  • A = Anxiety
  • M = Mechanical ventilation/ over ventilation
  • P = Progesterone
  • S = Salicylates / sepsis

Anaemia is a cause of tissue hypoxia.

Types of Hypoxias

  • Hypoxemic hypoxia.
  • Circulatory hypoxia.
  • Anaemic hypoxia.
  • Histotoxic hypoxia.

 Question 2:

From the history we can define features of high-risk syncope.

Any patient older than 65 should be admitted for inpatient ECHO. Mainly to exclude aortic stenosis. Also, exercise induced syncope is considered a high-risk syncope (Cardiomyopathy)

San Fracisco Syncope rule:

Patients with any of the following five “CHESS” predictors are considered are considered at risk of serious outcomes at 7 or 30 days

Mnemonic: CHESS

  1. Congestive heart failure
  2. Hematocrit <30%
  3. ECG abnormality
  4. Shortness of breath
  5. Systolic blood pressure <90 mmHg